This invention relates to optical devices, and more particularly to optical waveguide devices.
In the integrated circuit industry, there is a continuing effort to increase device speed and increase device densities. Optical systems are a technology that promise to increase the speed and current density of the circuits. Programmable delay generators are optical devices that are configured to delay light for a prescribed time. It is known to delay light using optical devices. For instance, light is reflected from Bragg gratings that are positioned to provide a prescribed round-trip distance, that corresponds to a prescribed round-trip delay. Optical delay generators can be discrete elements made from glass or clear plastic or alternatively can be formed from a semiconductor material, such as silicon.
Optical delay generators, as with most optical devices, are susceptible to changes in such operating parameters as temperature, device age, device characteristics, device age, device characteristics, contact, pressure, vibration, etc. As such, the optical delay generators are typically contained in packaging that maintains the parameters as desired. Providing such packaging is extremely expensive. Even if such packaging is provided, passive optical delay generators may be exposed to slight condition changes. Passive optical delay generators perform differently under different conditions. For example, an optical delay generator will delay light for a different delay period depending on the conditions, or may even not precisely delay light. If the characteristics of a passive optical delay generator is altered outside of very close tolerances, then the optical delay generator will not adequately perform its function. In other words, there is no adjustability to the passive optical delay generators.
As such it would be desirable to provide an optical delay generator that can controllably delay light. Additionally, it would be desirable to provide a mechanism to compensate in optical delay generators for variations in the operating parameters such as temperature and device age.
The present invention is directed to an apparatus and associated method for changing the propagation constant of a region of delaying propagation constant in an optical waveguide. The method comprising positioning an electrode of a prescribed electrode shape proximate the waveguide. A changeable region of delaying propagation constant is projected into the waveguide that corresponds, in shape, to the prescribed electrode shape by applying a voltage to the shaped electrode. The propagation constant level of the region of delaying propagation constant is controlled by varying the voltage. Light passing through the region of delaying propagation constant is delayed by a controllable amount.